Lymphocytes are much more common in the lymphatic system. The blood has three types of lymphocytes:
* B cells
: B cells make antibodies
that bind to pathogens to enable their destruction. (B cells not only make antibodies
that bind to pathogens, but after an attack, some B cells will retain the ability to produce an antibody to serve as a 'memory' system.)
* T cells:
* CD4+
(helper
) T cells co-ordinate the immune response and are important in the defence against intracellular bacteria.
* CD8+ cytotoxic T cells are able to kill virus-infected and tumor
cells.
* γδ T cells possess an alternative T cell receptor as opposed to CD4+ and CD8+ αβ T cells and share characteristics of helper T cells, cytotoxic T cells and natural killer cells.
* Natural killer cells: Natural killer cells are able to kill cells of the body which are displaying a signal to kill them, as they have been infected by a virus or have become cancerous
.